The family of Robert Levinson has released new images of the former FBI agent who was kidnapped in Iran in 2007.

The Levinson Family

The family of a former FBI agent who was kidnapped in Iran has released a new series of images of the 64-year-old man, showing him draped in chains and dressed in what appears to be a mock prison uniform. In each he holds a sign, one of which reads "Help me."

Robert Levinson was kidnapped while on a business trip to Iran's Kish Island in 2007. In the new images provided to ABC News and other outlets, the first made public since a 2010 "proof of life" video was released in December 2011, Levinson stares blankly into the camera for the five photos, his face framed by wild white hair and an unkempt white beard.

One of the signs makes reference to the U.S. government's detention camp in Guantanamo Bay, Cuba, where more than 160 suspected Taliban fighters and al Qaeda members are held. "I Am Here in Guantanamo Do You Know Where It Is?" reads the sign.

"This is the result of 30 years serving for USA," says another. "Why you can not help me. [sic]"

Authorities either do not know or have not publicly identified Levinson's suspected captors, but the U.S. government has repeatedly asked the Iranian government's help in finding him. The Associated Press reported that intelligence officials suspect the Iranian government, specifically its intelligence services, was behind the production of the proof of life video and new images.

The careful procedure -- or tradecraft in spy talk -- that the perpetrators used to get the images to Levinson's family without leaving any other trace was simply too good to be an amateur job, intelligence officials said, according to the AP.

Levinson's family has held the photos for months -- one of the signs apparently references his fourth year in captivity -- but his wife, Christine, told the AP she decided to release them to the public now because her husband's case wasn't getting enough attention from the government.

"There isn't any pressure on Iran to resolve this," she said. "It's been much too long."

During Iranian President Mahmoud Ahmadinejad's visit to the United Nations in New York in September 2012, Levinson's family blanketed Times Square with missing posters and ads for Levinson. During the same visit, Ahmadinejad hinted to CBS News that Levinson may have been in Iranian custody.

"I remember that last year Iranian and American intelligence groups had a meeting, but I haven't followed up on it," he said in response to a question about Levinson.

In March 2012, the FBI announced a $1 million reward for information leading to Levinson's safe return.

The release of the new photos came the same day another American family with a relative held in Iran announced they were planning a demonstration outside Iran's Permanent Mission to the United Nations.

On Wednesday, Amir Hekmati, a former U.S. Marine who was arrested by the Iranian government on espionage charges, will have been held in the Middle Eastern nation for 500 days. He was originally sentenced to death, but the Iranian government later ordered a retrial.

In an exclusive interview with ABC News shortly after his son's arrest was made public, Hekmati's father said that his son was no spy.

"My son is no spy. He is innocent. He's a good fellow, a good citizen, a good man," Hekmati said. "These are all unfounded allegations and a bunch of lies."